Pain relief in the chest due to fluid buildup may be a phenomenon caused by an increase in the amount of fluid in the chest. An increase in fluid accumulation in the chest often leads to a reduction in pain, but this does not mean a reduction in the condition. When the amount of fluid in the chest is small, the patient may experience a sharp stabbing pain due to the irritation of the pleural fluid and the mutual friction between the dirty pleura and the wall pleura. When the amount of fluid in the chest increases, due to the lubricating effect of pleural fluid, the friction between the dirty pleura and the wall pleura is weakened, so the pain is reduced, but this does not mean that the disease is reduced. Pleural fluid can be seen in tuberculous pleurisy, lung infection, pyothorax, heart failure, hypoproteinemia, metastasis of malignant tumors and other diseases. Increased pleural fluid can lead to chest tightness, palpitations, dyspnea, fever, fatigue and other symptoms. It is recommended that patients with pleural effusion go to the hospital in time to avoid delaying their condition.